Wednesday, March 2, 2011

Entomosporium Leaf Spot: The Fungus Among Us

As winter transitions into spring here in California, the temperatures rise, but the rains remain. You may be gardening in a short sleeved shirt, but your boots are still caked with mud.

Another unpleasant consequence of this combination of wet and warm: a leaf spot disease on many evergreen and deciduous plants, entomosporium.

If there is spotting on the leaves, and the leaves are falling, it could be entomosporium, a fungus that pops up during warm, wet, late winter-early spring weather.

Entomosporium on Photinia x fraseri

Entomosporium is a fungal disease that spots the leaves of plants in the Pomoideae group of the rose family, including apple, flowering crab apple, evergreen pear, hawthorn, pear, photinia (especially photinia!), pyracantha, quince, Rhaphiolepis (Indian hawthorn, among others), and toyon.

Indian Hawthorn with Entomosporium

According to the UC Davis Integrated Pest Management website, entomosporium appears as tiny reddish spots, sometimes surrounded by a yellow halo, appear on the leaves of infected plants, usually on older growth. These spots darken and enlarge as the leaves mature. Spore-forming bodies eventually appear in the center of the spots; these dark fruiting bodies may appear to be covered with a glossy membrane, beneath which white masses of spores may be visible. Infected plants may prematurely drop many leaves.

If that is the case, remove infected leaves from the ground and the shrub. Also, avoid overhead watering. Making sure there is room between the plants for good air circulation can help. If that is impractical, try removing some of the lower branches.

Toyon with entomosporium

Toyon / entomosporium

In overwhelming situations, the experts at UC say to remove any ground covers beneath the plant, which may harbor the fungus. It might not be a bad idea to replace any mulch that is there, as well.

• Isolated healthy plants or hedges can often remain healthy as the spores are only splashed over short distances. Space plants to improve the air movement around the plants and promote rapid drying of leaf surfaces.

• Do not water or fertilize plants any more than necessary to avoid promoting excess new growth.

• Reduce pruning during the summer which promotes continual new growth.

• It may be necessary to remove severely diseased plants and replace them with another plant species that is not susceptible to leaf spot. (Life is too short to put up with a problematic plant)

The good news: as drier weather takes hold here (and you avoid overhead watering), the entomosporium may go into hiding...until next year. Entomosporium fungi that infect deciduous plants overwinter mainly as spores on fallen leaves or as mycelia within tissue. On evergreen hosts, the fungi may remain on leaves year-round. Fungi are spread from infected tissue or contaminated leaf litter to healthy leaves by splashing raindrops or overhead irrigation. The pathogens are most severe during wet weather, especially when it coincides with new plant growth, according to UC.

In other words, the plant can tolerate it in most situations, if you help it along by a thorough cleanup of infected leaves and careful watering. The question is: can YOU tolerate it? In the larger scheme of all things horticultural, you have bigger bugs to battle.

10 comments:

I left them out on purpose. UC mentions Chlorothalonil as a preventative spray, but after checking the label of one such product, entomosporium is not even listed! UC mentions copper, but the product they mention, Microcop, is no longer available. Certain oil products that contain rosemary, garlic, clove, etc. may mention "leaf spot", but not entomosporium in particular. Sprays are only a preventative measure; they won't cure an existing situation. Cultural and physical controls should suffice for what is usually a nuisance problem. If entomosporium is that serious of a problem on a plant...get another plant.

If it affects apples & pears, does that mean it also affects Asian pear ? If I have it on photinia, will it affect the fruiting abilities of said Asian pear should it spread there ? Or is it really just cosmetic ?

It is more of a problem with evergreen ornamental pears. I don't recall a problem with entomosporium on my on Asian pears, and if it is there, it doesn't appear to degrade fruit quality. It would only be a problem if the effected leaves started dropping, thus reducing the fruit-producing vigor of the tree.

dear sir i have an 14 year old orchard of sandy pear grafted on quince. we use maximum fertigation through organic manures (FYM,Poultry). from last 3 years we stop fertigation beacuse of advice by some experts. one they bear at the age of eight. but their is very good blooming but the poblem is fruit set. in that area people use plum cultivation that is giving best yield without any care. but the problem is stroage and short life.few pear orchards are their but not in bearing so what is the solution and treatment for treas

My plants are suffering from this disease. My crepe myrtle which is in the middle of them died this winter and we live in Houston, Texas! All of the other crepes in this area are in full bloom!I wonder if this killed my crepe myrtle?

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